A compact hydraulic excavator generally used for civil engineering work in a city tends to be emphasized on its mobility when traveling between working sites since the operation period of the hydraulic excavator per working site is short, and therefore, a simply structured canopy being lightweight and having easily attachable/detachable two columns is mostly installed for protecting an operator's cab. However, in recent years, there are demand on enhancing the safeness for satisfying the unified strength standard, for instance the ROPS (Rollover Protective Structure) which is a strength standard prescribed in the ISO standard etc., even for the specification of canopies for assuring the safety of an operator in case of rollover accident of a vehicle.